Phenylketonuria (PKU) is a genetic deficiency of phenylalanine hydroxylase (PAH). Without PAH, the patient with PKU cannot metabolize phenylalanine (PHE) to tyrosine. The resulting accumulation of PHE and the accumulation of phenylpyruvate by a secondary metabolic pathway in the patient's blood produce neuropathies including severe mental retardation, behavioral problems, schizophrenia, and tremors. PKU treatment is tailored to keep plasma PHE concentrations between 2 and 6 mg/dl through a low-PHE diet and frequent blood monitoring. The invasiveness of this monitoring exposes the patient to infection risk, hypodermophobia (especially in children), plus the inconvenience and expense of performing invasive procedures and mailing or delivering the sample to the treatment center. We propose developing and commercializing a novel non-invasive, in-home monitoring device that can sample PHE through the patient's skin and correlate extracted PHE to blood concentrations with a high degree of accuracy and reproducibility using ACiont's proprietary reverse iontophoretic process. During development, we will team up with a bioengineering firm to develop a PHE biosensor for real-time, quantitative analysis. When complete, our device will allow patients to: easily perform the test and obtain results in a home setting, reduce clinic visit frequency by allowing result communications with clinicians over the internet, get real-time data with which to tailor treatment, decrease overall treatment costs through increased efficiency and elimination of third party laboratories, and drastically improve their control over PKU.